engineering question #3649

the answer

At the bottom inside the kettle there is an electric element. It contains a kind of wire that does not like passing electric current very much. When electricity from the plug in the wall goes into the kettle it goes through this wire and because the wire does not pass electric current very well, it offers a lot of resistance to the electrons and they get very agitated. This creates heat. The heat goes into the water and the water gets hotter until it boils. In modern kettles there's a temperature sensor that can tell when the water temperature reaches boiling and at this point it turns off the electricity to the heating element at the bottom.